A disk drive, such as a magnetic disk drive, comprises a magnetic disk, spindle motor, magnetic head, and carriage assembly. The magnetic disk is disposed in a case. The spindle motor supports and rotates the disk. The magnetic head reads and writes information from and to the disk. The carriage assembly supports the head for movement relative to the disk. The carriage assembly comprises a pivotably supported arm and a suspension extending from the arm, and a magnetic head is supported on an extended end of the suspension. The magnetic head comprises a slider mounted on the suspension and a head section disposed on the slider. The head section comprises a recording head for writing and a reproducing head for reading.
In recent years, a magnetic head for perpendicular magnetic recording has been proposed to increase the recording density and capacity or reduce the size of a magnetic disk drive. In the magnetic head of this type, a recording head comprises a main pole, return pole or write/shield pole, and coil. The main pole produces a perpendicular magnetic field. The return pole is located on the trailing side of the main pole with a write gap therebetween and closes a magnetic path between itself and a magnetic disk. The coil serves to pass magnetic flux through the main pole.
In recording a magnetic pattern along tracks of the magnetic disk, recording magnetic fields also leak out from the opposite sides of the machining pole transversely relative to the tracks. In order to reduce the leakage fields, a head is provided that comprises side shields on the opposite sides of the main pole transversely relative to the tracks. In order to enhance the recording density, moreover, a magnetic head of a radio-frequency-field-assisted recording type is proposed in which a spin-torque oscillator is provided between the main and return poles (e.g., Jpn. Pat. Appln. KOKAI Publications Nos. 2009-4089 and 2007-294059). In this head, the spin-torque oscillator applies a high-frequency magnetic head to a magnetic recording head.
If the shields are arranged individually on the opposite sides of the spin-torque oscillator in the magnetic head constructed in this manner, however, a magnetic field that flows into the oscillator is skewed in the vicinity of the film surface and transverse edges of the oscillator, thus failing to flow at right angles to the entire film surface. Consequently, the oscillation of the spin-torque oscillator is reduced, so that it is difficult to produce a desired high-frequency magnetic field.